Expansion bit



Sept. 17, 1940. A p ALBREHT 2,215,344

- EXPANSION BIT Filed April 25, 1939 (ALFRED P. ALBRECHI Patented Sept. 17, 1940 EXPANSION BIT Alfred P. Albrecht, Wilmington, Ohio, assignor to The Irwin Auger Bit Company, Wilmington, Ohio, a corporation of Ohio Application April .25, 1939, Serial No. 269,945

2 Claims;

This invention relates to an expansion bit which is provided with improved means for extending and retracting the extensible cutting element which determines the diameter of the hole to be bored.

It is the principal object of the present invention to provide in an expansion bit means for obtaining a micrometer adjustment of the ex- ,pansioncutter with one hand.

by rendering it necessary to out only a dove tail slot in the body of the bit near the boring end thereof, while at the same time providing a stronger assembly.

Still another object is to provide means for extending and retracting the expansion cutter which comprises a rack on the slidably mounted expansion cutter and a rotatable pinion mounted on the body of the bit and cooperating with the rackin such manner that as it is rotated the expansion cutter is moved laterally with respect to the bit. Indicia may be provided for indicating the lateral position of the expansion cutter and means is provided co-axial with the pinion for locking the pinion and thereby the expansion cutter without disturbing in the slightest the adjustment of the pinion and expansion cutter.

Still other objects will appear as the description of the invention proceeds.

Referring to the drawing:

Figure 1 is a front elevation of an expansion bit constructed in accordance with the present invention.

Figure 2 is a rear elevation of the bit of Figure 1.

Figure 3 is a plan view of the bit of Figures 1 and 2.

Figure 4 is a section on the line 4-4 of Figure 1, looking in the direction of the arrows.

Figure 5 is a perspective view showing the extensible cutting element and the adjusting micrometer in cooperating relationship.

Referring to the drawing in detail, reference numeral I generally designates the body of the bit provided with spur 2 and fixed cutting edge 3 on its enlarged end 4 which is somewhat greater than semi-cylindrical and which has a flat face 5.

Disposed transversely in the end 4 is a milled dove tail slot 6 which extends inwardly from face 5 and which is at a slightly oblique angle with respect to a plane normal to the axis of the bit.

This slot is formed by an unbroken face I which is'adjacent the cutting edge 3 and by a face 8 opposite face 1. Face 8 is broken in its middle for a purpose which will presently appear.

Face I is provided with a stepped portion 9 which extends outwardly and towards cutting edge 3.

Slidably disposed in slot 6 is the expansion cutter generally designated H] which is provided with cutting edge II which cuts that portion of the bottom of the hole not cut by constant cutting edge 3, and with cutting edge I2 which determines the diameter of the hole being bored.

Expansion cutter I is provided with a slanting side 13 which is adapted to cooperate in sliding engagement with broken slanting face 8 of slot 6, with a slanting side I4 which is adapted to cooperate with slanting face 1 of dove tail slot 6, and with a flat inward face l which is adapted to slidably engage the bottom fiat face 60, of slot 6. On the side next to cutting edge 3, the expansion cutter I0 is formed with a stepped'portion It which is adapted to engage slidably with step or shoulder 9 formed adjacent face 1 of slot 6. This stepped portion I6 tends to keep dust and chips from collecting between cutter l0 and slot 6. this stepped portion l6.

As a result of the construction of slot 6 and cutter Ill, these elements cooperate slidably and form a very strong assembly, cutter being firmly held from moving outwardly with respect to the body of the bit and operating therewith to prevent chips or dust from interfering with the slidable action desired.

Disposed on the face of the cutter In which is away from spur 2 is formed a rack Il extending parallel to the cutter. This rack comprises teeth l8 formed on slanting face I3 of cutter I0, the ends of the teeth being in the same plane with face l3 and the recesses forming the teeth extending towards the face I4 of the cutter.

Rotatably mounted with respect to body I is a pinion generally designated as l9 which is provided with teeth which cooperate with the teeth [8 of rack l'l. This pinion is in the form of a frustro-conical body, the teeth 20 extending the full length of the conical side which is equal to the depth of face I3. These teeth are formed.

over a semicircular arc of conical pinion 19 a1- C'utting edges II and I2 are form-ed on though obviously an arc of any other desired length may be employed.

Pinion I9 is mounted rotatably in a generally frustro-conical recess 2| formed inwardly of fiat face 5 of body 4. This pinion I9 is so formed that its slanting wall 24 is adapted to tightly frictionally engage the slanting wall of recess 2| before its flat inward face 22 engages the flat inward bottom face 23 of recess 2|, Thus it is insured that pinion I9 will tightly frictionally engage body 4 by reason of the wedging action of the slanting face 24 of pinion l9 against the slanting wall of recess 2| as it is drawn inwardly, and will thus be locked and lock cutter l0 firmly against motion relative to body 4.

Frustro-conical recess 2| is formed with an opening connecting it with slot 6. The bottom 23 of recess 2| is parallel to and lower than the bottom 6a of slot 6 in order to provide the clearance referred to above between face 22 of pinion l9 and face 23 of recess 2|. Through the opening thus formed between slot 6 and recess 2 several teeth of pinion |9 project into engagement with cooperating teeth l8 of rack H on cutter I0.

Thus, as pinion I9 is rotated about its own central axis, cutter Ill is moved to and fro in slot 6, in this way providing adjustment of the size of the hole bored by the bit.

Pinion I9 is provided with an integral outwardly extending knurled knob or dial 25 which is knurled on its periphery 25. Thus, by turning knob 25 with the fingers, pinion H3 is rotated and cutter I9 is slid in slot 6. In order to provide for firmly holding pinion IS in immovable relationship with respect to the body 4 of the bit I, a screw 26a extends from the rear of the body 4 through a hole 21 into screw-threaded engagement with a threaded hole in pinion l9 designated by 28. Thus, by loosening screw 26a slightly by means of a screw driver held in one hand, pinion I9 is freed of its frictional engagement with recess 2| and is free to be rotated with the other hand to the desired position when it may be secured in that position by tightening screw 26a so as to draw pinion l9 inwardly into tight frictional engagement with recess 2|.

By means of the rack and pinion, the operator is able to quickly secure a very accurate positioning of cutter l9. By reason of screw 26a, the operator is able to lock the assembly in any desired position without disturbing this predetermined accurate positioning of cutter ID. This result is partially brought about by the fact that screw 26a is co-axial with pinion I9. Screw 26a causes the pinion l9 to so tightly frictionally engage recess 2| as to overcome'any tendency of the rotation of screw 26a to rotate pinion I9 during the tightening. The force with which pinion I9 engages recess 2| is much greater than any force exerted by screw 26a tending to turn pinion l9 with itand to thereby disturb the adjustment of cutter Hi. In other words, the frictional force with which conoidal wall 24 engages recess 2| is at any instant of greater magnitude than and is developed before the frictional force with which the threads of screw 26a engage the threads in threaded hole 28 of pinion I9.

In order to allow a very accurate determination of the diameter of hole to be bored by the bit, pinion I9 is provided with a locating index 29 and the surrounding peripheral portion of body 4 is provided with angularly disposed indicia 3| which are calibrated in terms of the degree of extension of expansion cutter edge l2 or in terms of the radius or diameter of the hole to be bored. If desired, the single index 29 may be placed on the body 4 and the angularly disposed indicia 3| placed on the periphery of pinion I9.

It is pointed out that as pinion I9 is drawn inwardly by tightening screw 26a in pinion l9, pinion l9 exerts a force on cutter l0, pushing it towards the wall I, step 9 and even against wall 30 above step 9, thereby holding the cutter I0 firmly against any tendency to twist in slot 6. However, when pinion I9 is freed by loosening screw 26a, cutter I0 is freed from this binding action just mentioned and is free to readily slide in slot 6.

It will be understood that it is necessary to turn screw 26a only a few turns in order to free or tighten pinion I9 and consequently cutter l0. Yet screw 26a can be easily tightened with very little effort to such an extent that cutter I0 is held absolutely against movement of any kind relative to bit I.

As will be seen from the drawings, the mechanism for adjusting and locking cutter 10, namely screw 26a and pinion I9, is all located within a very small compass, in fact within the compass of the circle of the radius of body 4. Thus, the adjusting and locking mechanism clears the smallest hole which it may be desired to bore with the bit.

It will be understood that I desire to comprehend within my invention such modifications as may be necessary to adapt it to varying condtiions and uses.

Having thus fully described my invention, what I claim as new and desire to secure by Letters Patent is:

1. In an expansion bit, an expansion cutter which is laterally slidable with respect to the body of said bit and having a rack integrally formed thereon, a pinion the teeth of which engage said rack and which is rotatable with respect to the body of said bit, a gripping member integral with said pinion allowing said pinion to be readily rotated whereby to adjust the lateral position of said cutter, and a screw passing through said bit body from the opposite side thereof and screw-threadedly engaging said pinion axially therewith and adapted to lock said pinion in any-desired position of rotary adjustment, thereby locking said cutter in any desired position of lateral adjustment.

2. In an expansion bit, an expansion cutter which is laterally slidable with respect to the body of said bit and having a rack integrally formed thereon, a pinion the teeth of which engage said rack and which is rotatable with respect to the body ,of said bit, a knurled gripping member integral with said pinion allowing said pinion to be readily rotated whereby to adjust the lateral position of said cutter, and a screw passing through said bit body from the opposite side thereof and screw-threadedly engaging said pinion axially therewith and adapted to lock said pinion in any desired position of rotary adjustment, thereby locking said cutter in any desired position of lateral adjustment, said pinion having slanting conical walls and said bit body having slanting walls forming a conical recess cooperating with the slanting walls of said pinion to thereby cause said pinion to tightly frictionally engage said body portion-by reason of the wedging action of said pinion in said recess when said screw is operated in a direction to lock said pinion. ALFRED P. ALBRECHT. 

